package com.hua.utility.utility.tools;

/**
 * Base64 implements Base64 encoding and Base 64 decoding.
 *
 */

public class Base64 {

	private static byte[] Base64EncMap, Base64DecMap;

	static {
		// rfc-2045: Base64 Alphabet
		byte[] map = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G', (byte) 'H',
				(byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P',
				(byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X',
				(byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f',
				(byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
				(byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v',
				(byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3',
				(byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '+', (byte) '/' };
		Base64EncMap = map;
		Base64DecMap = new byte[128];
		for (int idx = 0; idx < Base64EncMap.length; idx++) {
			Base64DecMap[Base64EncMap[idx]] = (byte) idx;
		}
	}

	/**
	 * This method decodes the given byte[] using the base64-encoding specified
	 * in RFC-2045 (Section 6.8).
	 *
	 * @param data
	 *            the base64-encoded data.
	 * @return the decoded data.
	 */
	public final static byte[] base64Decode(byte[] data) {
		if (data == null) {
			return null;
		}

		int tail = data.length;
		while (data[tail - 1] == '=') {
			tail--;
		}

		byte dest[] = new byte[tail - data.length / 4];

		// ascii printable to 0-63 conversion
		for (int idx = 0; idx < data.length; idx++) {
			data[idx] = Base64DecMap[data[idx]];
		}

		// 4-byte to 3-byte conversion
		int sidx, didx;
		for (sidx = 0, didx = 0; didx < dest.length - 2; sidx += 4, didx += 3) {
			dest[didx] = (byte) (((data[sidx] << 2) & 255) | ((data[sidx + 1] >>> 4) & 003));
			dest[didx + 1] = (byte) (((data[sidx + 1] << 4) & 255) | ((data[sidx + 2] >>> 2) & 017));
			dest[didx + 2] = (byte) (((data[sidx + 2] << 6) & 255) | (data[sidx + 3] & 077));
		}
		if (didx < dest.length) {
			dest[didx] = (byte) (((data[sidx] << 2) & 255) | ((data[sidx + 1] >>> 4) & 003));
		}
		if (++didx < dest.length) {
			dest[didx] = (byte) (((data[sidx + 1] << 4) & 255) | ((data[sidx + 2] >>> 2) & 017));
		}

		return dest;
	}

	/**
	 * This method decodes the given string using the base64-encoding specified
	 * in RFC-2045 (Section 6.8).
	 *
	 * @param str
	 *            the base64-encoded string.
	 * @return the decoded str.
	 */
	public final static String base64Decode(String str) {
		if (str == null)
			return null;

		return new String(base64Decode(str.getBytes()));
	}

	/**
	 * This method encodes the given byte[] using the base64-encoding specified
	 * in RFC-2045 (Section 6.8).
	 *
	 * @param data
	 *            the data
	 * @return the base64-encoded data
	 */
	public final static byte[] base64Encode(byte[] data) {
		if (data == null) {
			return null;
		}

		int sidx, didx;
		byte dest[] = new byte[((data.length + 2) / 3) * 4];

		// 3-byte to 4-byte conversion + 0-63 to ascii printable conversion
		for (sidx = 0, didx = 0; sidx < data.length - 2; sidx += 3) {
			dest[didx++] = Base64EncMap[(data[sidx] >>> 2) & 077];
			dest[didx++] = Base64EncMap[(data[sidx + 1] >>> 4) & 017 | (data[sidx] << 4) & 077];
			dest[didx++] = Base64EncMap[(data[sidx + 2] >>> 6) & 003 | (data[sidx + 1] << 2) & 077];
			dest[didx++] = Base64EncMap[data[sidx + 2] & 077];
		}
		if (sidx < data.length) {
			dest[didx++] = Base64EncMap[(data[sidx] >>> 2) & 077];
			if (sidx < data.length - 1) {
				dest[didx++] = Base64EncMap[(data[sidx + 1] >>> 4) & 017 | (data[sidx] << 4) & 077];
				dest[didx++] = Base64EncMap[(data[sidx + 1] << 2) & 077];
			} else
				dest[didx++] = Base64EncMap[(data[sidx] << 4) & 077];
		}

		// add padding
		for (; didx < dest.length; didx++) {
			dest[didx] = (byte) '=';
		}

		return dest;
	}

	/**
	 * This method encodes the given string using the base64-encoding specified
	 * in RFC-2045 (Section 6.8).
	 *
	 * @param str
	 *            the string
	 * @return the base64-encoded str
	 */
	public final static String base64Encode(String str) {
		if (str == null) {
			return null;
		}
		return new String(base64Encode(str.getBytes()));
	}
}
